The rate of a first order reaction is $0.04 mol \, l^{-1} \, s^{-1}$ at 10 seconds and $0.03 \, mol \, l^{-1} \, s^{-1}$ at 20 seconds after initiation of the reaction. The half-life period of the reaction is :
- 34.1 s
- 44.1 s
- 54.1 s
- 24.1 s
The Correct Option is D
Solution and Explanation
Calculation of Half-Life
We are given the equation for the rate constant K as:
\(K = \frac{2.303}{10} \log \frac{0.04}{0.03}\)
Now, simplifying the logarithmic expression:
\(K = \frac{2.303}{10} \log \frac{4}{3}\)
Using the logarithmic value:
\(K = \frac{2.303 \times 0.123}{10}\)
Now, calculate K:
\(K = 0.0285\)
The half-life t1/2 is calculated using the formula:
\(t_{1/2} = \frac{0.693}{K}\)
Substitute the value of K into the equation:
\(t_{1/2} = \frac{0.693}{0.0285} = 24.1 \, \text{s}\)
Thus, the half-life is 24.1 seconds.
Top Questions on Chemical Kinetics
- Correct statements regarding Arrhenius equation among the following are:
Factor \(e^{-E_a/RT}\) corresponds to fraction of molecules having kinetic energy less than \(E_a\).
At a given temperature, lower the \(E_a\), faster is the reaction.
Increase in temperature by about \(10^\circ\text{C}\) doubles the rate of reaction.
Plot of \(\log k\) vs \(\dfrac{1}{T}\) gives a straight line with slope \(= -\dfrac{E_a}{R}\).
Choose the correct answer from the options given below:- JEE Main - 2026
- Chemistry
- Chemical Kinetics
- Decomposition of A is a first order reaction at T(K) and is given by \( A(g) \rightarrow B(g) + C(g) \).
In a closed 1 L vessel, 1 bar A(g) is allowed to decompose at T(K). After 100 minutes, the total pressure was 1.5 bar. What is the rate constant (in \( min^{-1} \)) of the reaction ? (\( \log 2 = 0.3 \))- JEE Main - 2026
- Chemistry
- Chemical Kinetics
- An organic compound undergoes first order decomposition. The time taken for decomposition to \(\dfrac{1}{8}\) and \(\dfrac{1}{10}\) of its initial concentration are \(t_{1/8}\) and \(t_{1/10}\) respectively. Find the value of \[ \frac{t_{1/8}}{t_{1/10}}\times10 \] (Given: \(\log 2 = 0.3\))
- JEE Main - 2026
- Chemistry
- Chemical Kinetics
Consider the following compounds. Arrange these compounds in a n increasing order of reactivity with nitrating mixture. The correct order is :
- JEE Main - 2026
- Chemistry
- Chemical Kinetics
- At $27^\circ\text{C}$, in presence of a catalyst, activation energy of a reaction is lowered by $10\,\text{kJ mol}^{-1}$. The logarithm of the ratio $\dfrac{k(\text{catalysed})}{k(\text{uncatalysed})}$ is ___.
(Consider that the frequency factor for both the reactions is same)
- JEE Main - 2026
- Chemistry
- Chemical Kinetics
Questions Asked in NEET exam
- Two cities X and Y are connected by a regular bus service with a bus leaving in either direction every T min. A girl is driving scooty with a speed of 60 km/h in the direction X to Y. She notices that a bus goes past her every 30 minutes in the direction of her motion, and every 10 minutes in the opposite direction. Choose the correct option for the period T of the bus service and the speed (assumed constant) of the buses.
- NEET (UG) - 2025
- Relative Velocity
- A physical quantity P is related to four observations a, b, c, and d as follows: P = a3 b2 (c / √d) The percentage errors of measurement in a, b, c, and d are 1%, 3%, 2%, and 4% respectively. The percentage error in the quantity P is:
- NEET (UG) - 2025
- Dimensional analysis and its applications
What is Microalbuminuria ?
- NEET (UG) - 2025
- Human physiology
The output (Y) of the given logic implementation is similar to the output of an/a …………. gate.
- NEET (UG) - 2025
- Logic gates
- An oxygen cylinder of volume 30 litre has 18.20 moles of oxygen. After some oxygen is withdrawn from the cylinder, its gauge pressure drops to 11 atmospheric pressure at temperature \(27^\circ\)C. The mass of the oxygen withdrawn from the cylinder is nearly equal to: [Given, \(R = \frac{100}{12} \text{ J mol}^{-1} \text{K}^{-1}\), and molecular mass of \(O_2 = 32 \text{ g/mol}\), 1 atm pressure = \(1.01 \times 10^5 \text{ N/m}^2\)]
- NEET (UG) - 2025
- Ideal-gas equation and absolute temperature
Concepts Used:
Chemical Kinetics
Chemical kinetics is the description of the rate of a chemical reaction. This is the rate at which the reactants are transformed into products. This may take place by abiotic or by biological systems, such as microbial metabolism.
Rate of a Chemical Reaction:
The speed of a reaction or the rate of a reaction can be defined as the change in concentration of a reactant or product in unit time. To be more specific, it can be expressed in terms of: (i) the rate of decrease in the concentration of any one of the reactants, or (ii) the rate of increase in concentration of any one of the products. Consider a hypothetical reaction, assuming that the volume of the system remains constant. R → P
Read More: Chemical Kinetics MCQ
Factors Affecting The Reaction Rate:
- The concentration of Reactants - According to collision theory, which is discussed later, reactant molecules collide with each other to form products.
- Nature of the Reactants - The reaction rate also depends on the types of substances that are reacting.
- Physical State of Reactants - The physical state of a reactant whether it is solid, liquid, or gas can greatly affect the rate of change.
- Surface Area of Reactants - When two or more reactants are in the same phase of fluid, their particles collide more often than when either or both are in the solid phase or when they are in a heterogeneous mixture. In a heterogeneous medium, the collision between the particles occurs at an interface between phases. Compared to the homogeneous case, the number of collisions between reactants per unit time is significantly reduced, and so is the reaction rate.
- Temperature - If the temperature is increased, the number of collisions between reactant molecules per second. Increases, thereby increasing the rate of the reaction.
- Effect Of Solvent - The nature of the solvent also depends on the reaction rate of the solute particles.
- Catalyst - Catalysts alter the rate of the reaction by changing the reaction mechanism.